1. Field of the Invention
The present invention relates to medical syringes and, more particularly, is directed to syringe systems adapted for use in connection with pre-filled medicament cartridges and methods for maintaining the sterility of such systems prior to use.
2. Description of the Invention Background
Hypodermic syringes are used for a variety of injection procedures including the delivery of medicinal drugs to a recipient. A typical hypodermic syringe arrangement may include a hollow syringe body that has a double-ended needle or cannula attached to one end of the tube. One end of the cannula usually protrudes from the syringe body for insertion into a patient or suitable port and is protected prior to use by a removable sheath. The other end of the cannula extends into the hollow syringe body for engagement with a cartridge that has been pre-filled with medicament.
The cartridge typically comprises a glass tube that is sealed at one end with a pierceable membrane usually fabricated from rubber. The other end of the cartridge is sealed by a plunger member that is slidably mounted within the cartridge tube. The cartridge is inserted into the open end of the syringe body until the inwardly protruding cannula pierces through the rubber seal. A plunger rod is then inserted through the open end of the syringe body to engage the plunger located in the cartridge. The sheath is removed from the outer end of the cannula to enable it to be inserted into a patient or port. The medicament is discharged through the cannula by axially pushing the plunger rod and plunger towards the cannula. In instances wherein it is desirable to use the syringe as an aspirator, the plunger rod is fastened to the plunger to enable the plunger to be pulled towards the rear end of the cartridge. Such movement of the plunger will cause body fluids to be drawn into the cartridge through the cannula.
A great majority of syringes used today are disposable to prevent the spread of infectious diseases from the reuse of contaminated syringes. The syringe components (i.e., the syringe body/cannula assembly, cannula sheath and plunger rod) are sterilized and packaged in an airtight sterile package for shipment to the end user. Because the syringes are discarded after a single use, it is desirable to minimize their cost.
Over the years, syringe manufacturers have developed various innovative syringe designs that utilize relatively low cost plastics in an effort to make the use of disposable syringes a safe and economically viable alternative to using reusable syringes that must be re-sterilized prior to each use. For example, U.S. Pat. No. 2,693,803 to Ogle discloses a disposable pre-filled syringe which has a plunger rod that functions as a needle sheath prior to use. The syringe body houses the medicament and is sealed on one end by a plunger and the plunger rod serves to encase the end of the needle when it is pressed onto the front of the syringe body. However, these disposable syringe arrangements are ill-suited for use with separate pre-filled medicament cartridges which may be supplied by a host of different suppliers. Also, because the plunger rod is only pressed onto the front of the syringe, it is susceptible of being jarred loose during shipping which could compromise the syringe's sterility. Similar syringe designs are disclosed in U.S. Pat. No. 2,616,420 to Hart, U.S. Pat. No. 2,662,740 to Hickey, U.S. Pat. No. 2,880,723 to Adams, U.S. Pat. No. 3,375,825 to Keller, U.S. Pat. No. 3,534,734 to Budreck and U.S. Pat. No. 3,783,997 to Brown.
Another syringe arrangement is disclosed in U.S. Pat. No. 2,728,341 to Roehr. That arrangement employs a hollow plunger rod for storing a detachable hub mounted cannula. A sterile stopper must be inserted in the open end of the plunger rod to maintain the sterility of the cannula prior to use. While this syringe arrangement is constructed for use with a pre-filled cartridge, it requires the application of a sterile stopper to the open end of the plunger rod to maintain the sterility of the cannula prior to use.
Other syringes that are adapted for use with pre-filled cartridges are disclosed in U.S. Pat. No. 2,826,195 to Ashkenaz, U.S. Pat. No. 4,808,169 to Haber et al. and Patent Cooperation Treaty Application Serial No. PCT/US88/03316 to Habley Medical Technology Corporation. In each of those syringe designs, the plunger rod is adapted to alternatively serve as a needle sheath prior to use. However, to maintain the sterility of these syringes prior to use, they must be packaged in airtight sterile packages.
In addition, medications adapted to be administered by means of injection through a needle or cannula are designed for introduction into a patient's system in a specific manner. Certain medications must not be injected into a patient's vein or artery. Instead, some types of medications are adapted to be injected intramuscularly or subcutaneously. When medications are administered subcutaneously or intramuscularly, the injection device is typically aspirated after the cannula has been injected into the patient. During such aspiration, the user observes the rear end of the cannula through the transparent syringe barrel. If the forward point of the cannula has penetrated a vein or artery, blood will immediately appear in that area. With many hypodermic devices and medications, the foregoing procedure presents little or no problems with detecting the presence of blood. However, with certain medications such as those comprising translucent or opaque medicaments, visual detection of blood presents somewhat of a problem or at least an inconvenience since an excessive amount of blood must be withdrawn through the cannula before it becomes detectable. This problem is also commonly encountered with the syringe designs discussed above.
Thus, all of the above-mentioned syringe designs have various shortcomings. While some of those syringes do not have to be packaged in airtight sterile packages to maintain their sterility prior to use, they are ill-suited for use with separate cartridges that are pre-filled with medicament. Also, while some of the above-mentioned cartridges are specifically adapted for use in connection with separate pre-filled cartridges, they must be packed in sterile airtight packages prior to use to prevent them from becoming contaminated. Moreover, while some of the prior syringes can be used for aspiration purposes, they lack means for quickly detecting the presence of blood during aspiration.
Accordingly, there is a need for a syringe system that is adapted for use in connection with separate pre-filled medicament cartridges that do not have to be packaged in airtight packages to maintain their sterility prior to use.
There is a further need for a syringe system with the above-mentioned attributes that can be easily adapted for use in connection with a variety of different ports.
There is yet another need for a syringe that can be used for aspiration purposes that is equipped with means or quickly detecting the presence of blood during aspiration.